Memory loss and confusion have long been recognized as possible consequences of aging. However, it was not until 1910 that the term Alzheimer's disease (AD) was first used to describe individuals with progressive intellectual deterioration. The condition was named after Dr. Alois Alzheimer, who, in 1906, described the unique changes within the brain that remain diagnostic for Alzheimer's disease.

Our understanding of AD has evolved significantly since Dr. Alzheimer's time. Alzheimer's disease is now considered an age-related brain disorder caused by the injury and death of nerve cells in particular areas of the brain. It is also now recognized as the most common form of dementia, a term used by doctors to describe a syndrome of multiple intellectual deficits that has many different causes.

Alzheimer's disease is always characterized by progressive intellectual deterioration. This includes not only memory loss, which is usually the most prominent feature of Alzheimer's disease, but also changes in language and spatial orientation. For example, even in the early stages of Alzheimer's disease, individuals may have difficulty with finding words in conversation or may get lost in unfamiliar environments. Alzheimer's disease is also frequently associated a variety of psychiatric and behavioural signs, such as depression or personality changes, although these are not always present.

The initial intellectual changes of Alzheimer's disease are usually subtle, and it may be difficult to accurately date their precise onset. However, all people with the disease eventually become profoundly impaired and completely dependent upon others for even the most basic activities.